What does Blackwell Companion mean?

Context:

Carroll is an atheist. He turned down an invitation to speak at a conference sponsored by the John Templeton Foundation, on the grounds that he did not want to appear to be supporting a reconciliation between science and religion.[11] In 2004, he and Shadi Bartsch taught an undergraduate course title at the University of Chicago on the history of atheism. In 2012 he organized the workshop "Moving Naturalism Forward", which brought together scientists and philosophers to discuss issues associated with a naturalistic worldview. His article, "Does the Universe Need God?" in The Blackwell Companion to Science and Christianity develops the claim that science no longer needs to posit a divine being to explain the existence of the universe. The article generated significant attention when it was discussed on The Huffington Post.[12]

MOre:
https://en.wikipedia.org/wiki/Sean_M._Carroll#Views_on_religion